diff --git a/taiga/mdrender/extensions/mentions.py b/taiga/mdrender/extensions/mentions.py
index 0664bd94..83eeae20 100644
--- a/taiga/mdrender/extensions/mentions.py
+++ b/taiga/mdrender/extensions/mentions.py
@@ -32,7 +32,7 @@ from taiga.users.models import User
 
 class MentionsExtension(Extension):
     def extendMarkdown(self, md, md_globals):
-        MENTION_RE = r'(@)([a-z0-9.-\.]+)'
+        MENTION_RE = r'(@)([a-zA-Z0-9.-\.]+)'
         mentionsPattern = MentionsPattern(MENTION_RE)
         mentionsPattern.md = md
         md.inlinePatterns.add('mentions', mentionsPattern, '_end')
diff --git a/tests/integration/test_mdrender.py b/tests/integration/test_mdrender.py
index 3735eac2..6710a014 100644
--- a/tests/integration/test_mdrender.py
+++ b/tests/integration/test_mdrender.py
@@ -47,6 +47,12 @@ def test_render_and_extract_mentions():
     (_, extracted) = render_and_extract(dummy_project, "**@user1**")
     assert extracted['mentions'] == [user]
 
+def test_render_and_extract_mentions_with_capitalized_username():
+    user = factories.UserFactory(username="User1", full_name="test")
+    (_, extracted) = render_and_extract(dummy_project, "**@User1**")
+    assert extracted['mentions'] == [user]
+
+
 def test_proccessor_valid_email():
     result = render(dummy_project, "**beta.tester@taiga.io**")
     expected_result = "<p><strong><a href=\"mailto:beta.tester@taiga.io\" target=\"_blank\">beta.tester@taiga.io</a></strong></p>"